Perhaps many of us had to visit at least once in the interview. And if instead of the usual questions on summary and specifics of the applicant hears the riddle, the memories will be unforgettable. And it was like the «highlight» found in the interview such famous companies as Apple, Google, and Microsoft.

### 1. The riddle about the two doors

The riddle of the selection problem. /Photo: tyt.byЭту problem can be heard in the walls of the digital giant Apple. The condition reads:»Sheldon Cooper (character in the popular TV series) was a game until the last turn. Now before him two doors, one of which will lead to the treasure and the other in a deadly maze. At each door stands a guard, both of them know which one leads to the treasure. That’s only one of them will tell the truth. Sheldon does not know who is the liar and who is not. Before you make a choice, you can put only one question to only one guard.Question: What do I need to ask Sheldon the guard to find a way to the treasure?»Answer: you Can ask any of formulating the question: «What is the door, according to another guard, right?». If he asks the «truth-teller», it finds out which door leads to the labyrinth, lying because the guard always lies. If he were to ask the liar, then again finds out which door leads to the maze, because he will lie about the doors, which will indicate a true guard.

### 2. Aliens and caps

The confrontation of alien conquest. /Photo:. read more netЕще one mystery for job seekers in the Apple. It sounds like this:»the Earth is invaded by aliens. They want to destroy the entire planet, but decided to give mankind one more chance. They chose ten of the most intelligent people and put them in a completely dark room, lined up. Each put on the hat, the hat is two colors — white and black. After all the hats are on their heads, the light turns on.The alien asks the last person in the row of the color of his hat. About anything except the color of the hat, you can not ask, as to remain silent. If he answers right, remains alive, is wrong — dies. The color of the hat to you, but it is possible to agree about a particular principle that can answer all. The location of hat — random, but you can see all the hats in front.Question: What’s the answer to survived as many people as possible?»Answer: the First meet counts the number of black hats in front of him, if their is an odd number, he calls «black» if the number is even «white». Following seeing the hats before him, can thus calculate what color headdress on his head (for example, if black is still an odd number, it is obvious that it is white), and so on. This method saved 9 out of 10 people.

### 3. The job with motorcycles

Fifty motorcycles and an endless road ahead. /Photo: motorpage.geta task is a frequent guest interviews from Adobe:»you Have fifty motorcycles a full tank of petrol which is enough for 100 km drive.Question: How far you can go with these fifty motorcycles (given that initially they are conventionally one point)?Answer: First, you need to move all the motorcycles to fifty kilometers. Then, the fuel half motorcycle perebivaetsya in the second half. As a result, we have 25 motorcycles with a full tank. Repeat the procedure every fifty kilometers. Thus, it is possible to travel 350 km.

### 4. The problem of two buckets

When you need a happy medium, and to hand buckets of different sizes. /Photo: teletype.pri the selection of future employees at Microsoft use the following task:»you Have an infinite supply of water and two buckets of 5 liters and 3 liters respectively.Question: How do we use them to measure out four litres?»Answer: First fill a five-gallon bucket and pour some water in a glass. Now in a large bucket of two liters. Empty the small bucket and pour it with water from big. Again fill a big bucket and pour water from it in the least. Since it already has 2 liters, and after transfusion in a large 4 liter will remain.

### 5. The mystery about the two burning ropes

How to use the ropes to count the time. /Photo: mixstuff.generyczna task from the walls of Microsoft offices:»you Have two segments of rope. The length of each of them is such that when ignited any of them from one end it will burn in exactly sixty minutes.Question: With only a box of matches, how to measure using two lines like this rope for 45 minutes, provided that the tear rope bad?»A: One of the ropes ignited from both ends, at the same time it ignited the second, but with one end. When the first segment burns out, it would be 30 minutes, from the first also remains the 30-minute period. Then ignite the remaining rope from both ends, and it burns for another 15 minutes.

### 6. The problem of eight balls

One size does not mean one weight. /Photo: zagadky.computevalue that the information giant like Google, which is able to generate any information, there are puzzles for interviews. The condition is:»you Have 8 balls of the same type and size.Question: How to find the heavier ball provided that you can use the scale only twice?»Answer: Collect six balls, divide them into groups of three ball and place on the scales. Those with a heavier ball, win the Cup. Select from this group any two balls and weigh again. If the heavy ball is among them, you will see it if they weigh equally heavy is the third ball of the group. If the heavier ball in groups of 3 ball was not there, he’s among the 2 remaining.

### 7. Life hack for interviews from Elon musk

Mystery-a favorite of Elon musk. /Photo: mk.yokazuna have Elon musk have their own favorite mystery on case interviews. The conditions are as follows:»Imagine that you are standing on the Earth’s surface. You walk one mile South, one West and one North and end up at the same point where we started the movement.Question: Where are you?»Answer: there are two. The first one is able to give the majority of engineers is the North pole. If from the North pole, go one mile South, then turn West and walk another mile, and then changed direction to North, then after one mile you will be back at the North pole, closing by the movement of the triangle.The second correct answer to the riddle — the South pole, one mile North of the parallel, the length of which is equal to one mile.

### 8. Task-bonus

A great scholar and today encourages active brain activity. /Photo: facebook.soma this objective we offer you to decide for yourself. It is interesting one of its history: its alleged authors name not albert Einstein, not that of Lewis Carroll.»On the street there are five houses.The Englishman lives in the red house.The Spaniard has a dog.In the green house drink coffee.The Dane drinks tea.The green house is immediately to the right of the white house.Anyone who smokes Old Gold, breeds snails.In the yellow house smokes Kool.In the Central house drink milk.The Norwegian lives in the first house.A neighbor who smokes Chesterfield, is holding a Fox.In the house next to that in which the horse is kept, smoke Kool.Anyone who smokes Lucky Strike, drinking orange juice.The Japanese smokes Parliament.The Norwegian lives next to blue house.Each house has a different color, in each house lives a representative of a certain nationality, each of your pet, its favorite brand of cigarettes and drink.Question: Who drinks water? Who owns the Zebra?»